A serum antibody is an antibody derived from serum, a blood component that is collected after blood has coagulated. As it is collected after coagulation, blood serum does not actually contain blood cells or clotting factors. It does, however, include many different types of proteins that are not involved in the clotting process, including antibodies. Antibodies, or immunoglobulins, are specialized proteins that make up a primary component of the immune system by recognizing and, ideally, disabling foreign bodies, including viruses, bacteria, and other illness-causing agents. It is often necessary to isolate a particular serum antibody from animals for research purposes or from people for purposes of diagnosis or treatment.
There are many different processes in biomedical and biological research that require researchers to isolate a particular antibody from an animal, such as a mouse, rat, goat, or sheep. To gather these antibodies, researchers inject the animal with a specific antigen, or foreign body, that will promote the formation of specific antibodies designed to bind to and disable the antigen. Blood serum containing the antibodies is then collected from the animals. At this point, the substance is generally referred to as "antiserum" because of the emphasis on the antibodies it contains.
An isolated type of antibody or, in some cases, a group of different serum antibodies are useful in several different types of experiments. The antibodies can, for instance, be "tagged" with fluorescent or easily-recognizable protein markers before being introduced to a blood or tissue sample. The prevalence of a specific antigen can be judged based on the amount of tagged antibody present on the sample. It is important to note that antibodies are highly specific; animals and humans produce specific antibodies to bind to specific antigens. This specificity means that there is generally very little nonspecific binding, so the prevalence of the marked proteins can be taken as a reasonably sure sign of the presence of the antigen of interest.
Antiserum, or blood serum containing an antibody that targets a specific antigen, can also be used as a direct method of treatment. Some diseases are only able to strongly affect individuals who exhibit little immune response. The nature of the individual's immune system or of the disease itself may make it difficult for the necessary immune response to occur. Serum containing the necessary antibody can be transferred from one individual to another. The antibody can fight the illness and can help promote the afflicted individual's natural immune response.